I just wanted to add to moonboots tip, which i think is good, but i think can be a little clearer. : ) 

Select you object in Edit Mode. Use <kbd>Ctrl</kbd> + <kbd>R</kbd> to add edge loops (mouse wheel to increase/decrese the number of edge loops). Then mouse click, slide (if needed), and click again to confirm. If you put two edge loops close to each other you have a loop of faces, which can be the basis for your ridge. 

<kbd>Alt</kbd> + mouse click a face in the loop to select the whole loop. (if it selects faces in a perpendicular direction, click closer to another edge of the face)

With your faces-loop selected, press <kbd>Alt</kbd> + <kbd>E</kbd> and choose Extrude Faces Along Normals, and extrude the ridge.

Instead of a Subdivision Surface modifier (that moonboots proposed) i would use an Edge Split Modifier, since I believe the section of the ridges on such a nozzle is square. An Edge Split Modifier will help pronounce this while the rest of the nozzle stays smooth.